412 



THE ORGANS OF SPECIAL SENSE 



The cochlea resembles a snail shell. Its apex looks 

 forward and outward, and its base toward the internal 

 auditory meatus. Within is a centre piece, the modiolus 

 or columella, around which the canal runs spirally for 

 two and one-half turns. 



Within the canal, and attached to the modiolus, is 

 the lamina spiralis. This plate of bone partially 

 divides the spiral canal into two compartments or 

 scalse, the division being completed by a membrane 



Fro. 144 



ENDOLYMPHATIC CANAL 



CANALIS 

 REUNIENS 



Membranous labyrinth of the right ear, viewed from the outer side; 

 semidiagrammatic. (Testut.) 



which reaches the outer wall of the cochlea. The 

 upper scala is known as the scala vestibuli; the lower 

 is the scala tympani. 



The membranous labyrinth is contained within the 

 osseous labyrinth, having a similar form, though 

 smaller and separated from it by the perilymph. It 

 contains the endolymph and receives the distribution 

 of the auditory nerve. In the vestibule it consists of 

 the utricle and the saccule. 



The membranous semicircular canals are similar in 

 shape to, but are only from one-fifth to one-third the 



